package com.platform.common.util.encrypt;

import javax.crypto.Cipher;
import javax.crypto.KeyAgreement;
import javax.crypto.SecretKey;
import javax.crypto.interfaces.DHPrivateKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
 * DH Diffie-Hellman算法(D-H算法)，密钥一致协议
 * @author liuli
 * 流程分析： 

1.甲方构建密钥对儿，将公钥公布给乙方，将私钥保留；
	双方约定数据加密算法；乙方通过甲方公钥构建密钥对儿，将公钥公布给甲方，将私钥保留。 
2.甲方使用私钥、乙方公钥、约定数据加密算法构建本地密钥，然后通过本地密钥加密数据，发送给乙方加密后的数据；
	乙方使用私钥、甲方公钥、约定数据加密算法构建本地密钥，然后通过本地密钥对数据解密。 
3.乙方使用私钥、甲方公钥、约定数据加密算法构建本地密钥，然后通过本地密钥加密数据，发送给甲方加密后的数据；
	甲方使用私钥、乙方公钥、约定数据加密算法构建本地密钥，然后通过本地密钥对数据解密。 

 *
 */
public abstract class DHCoder extends Coder {
	
	public static void main(String[] args) {
		try {
			// 生成甲方密钥对儿  
	        Map<String, Object> aKeyMap = DHCoder.initKey();
	        String aPublicKey = DHCoder.getPublicKey(aKeyMap);
	        String aPrivateKey = DHCoder.getPrivateKey(aKeyMap);
	        System.err.println("甲方公钥:\r" + aPublicKey);  
	        System.err.println("甲方私钥:\r" + aPrivateKey);  
	        // 由甲方公钥产生本地密钥对儿  
	        Map<String, Object> bKeyMap = DHCoder.initKey(aPublicKey);
	        String bPublicKey = DHCoder.getPublicKey(bKeyMap);
	        String bPrivateKey = DHCoder.getPrivateKey(bKeyMap);
	        System.err.println("乙方公钥:\r" + bPublicKey);  
	        System.err.println("乙方私钥:\r" + bPrivateKey);  
	        String aInput = "abc ";  
	        System.err.println("原文: " + aInput);  
	        // 由甲方公钥，乙方私钥构建密文  
	        byte[] aCode = DHCoder.encrypt(aInput.getBytes(), aPublicKey,bPrivateKey);
	  
	        // 由乙方公钥，甲方私钥解密  
	        byte[] aDecode = DHCoder.decrypt(aCode, bPublicKey, aPrivateKey);
	        String aOutput = (new String(aDecode));  	  
	        System.err.println("解密: " + aOutput);    
	        System.err.println(" ===============反过来加密解密================== ");  
	        String bInput = "def ";  
	        System.err.println("原文: " + bInput);  	  
	        // 由乙方公钥，甲方私钥构建密文  
	        byte[] bCode = DHCoder.encrypt(bInput.getBytes(), bPublicKey,aPrivateKey);
	        // 由甲方公钥，乙方私钥解密  
	        byte[] bDecode = DHCoder.decrypt(bCode, aPublicKey, bPrivateKey);
	        String bOutput = (new String(bDecode));  
	        System.err.println("解密: " + bOutput);  
	        
	        
		} catch (Exception e) {
			System.out.println(e.getMessage());
		}
	}
	  public static final String ALGORITHM = "DH";
	  /** 
	     * 默认密钥字节数 
	     *  
	     * <pre> 
	     * DH 
	     * Default Keysize 1024   
	     * Keysize must be a multiple of 64, ranging from 512 to 1024 (inclusive). 
	     * </pre> 
	     */  
	    private static final int KEY_SIZE = 1024;  
	    /** 
	     * DH加密下需要一种对称加密算法对数据加密，这里我们使用DES，也可以使用其他对称加密算法。 
	     */  
	    public static final String SECRET_ALGORITHM = "DES";  
	    private static final String PUBLIC_KEY = "DHPublicKey";  
	    private static final String PRIVATE_KEY = "DHPrivateKey";  
	    /** 
	     * 初始化甲方密钥 
	     *  
	     * @return 
	     * @throws Exception 
	     */  
	    public static Map<String, Object> initKey() throws Exception {  
	        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);  
	        keyPairGenerator.initialize(KEY_SIZE);  
	        KeyPair keyPair = keyPairGenerator.generateKeyPair();  
	        // 甲方公钥  
	        DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();  
	        // 甲方私钥  
	        DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();  
	        Map<String, Object> keyMap = new HashMap<String, Object>(2);  
	        keyMap.put(PUBLIC_KEY, publicKey);  
	        keyMap.put(PRIVATE_KEY, privateKey);  
	        return keyMap;  
	    }  
	  
	    /** 
	     * 初始化乙方密钥 
	     *  
	     * @param key 
	     *            甲方公钥 
	     * @return 
	     * @throws Exception 
	     */  
	    public static Map<String, Object> initKey(String key) throws Exception {  
	        // 解析甲方公钥  
	        byte[] keyBytes = decryptBASE64(key);  
	        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);  
	        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);  
	        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);  
	        // 由甲方公钥构建乙方密钥  
	        DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();  
	        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(keyFactory.getAlgorithm());  
	        keyPairGenerator.initialize(dhParamSpec);  
	        KeyPair keyPair = keyPairGenerator.generateKeyPair();  
	        // 乙方公钥  
	        DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();  
	        // 乙方私钥  
	        DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();  
	        Map<String, Object> keyMap = new HashMap<String, Object>(2);  
	        keyMap.put(PUBLIC_KEY, publicKey);  
	        keyMap.put(PRIVATE_KEY, privateKey);  
	  
	        return keyMap;  
	    }  
	  
	    /** 
	     * 加密<br> 
	     *  
	     * @param data 
	     *            待加密数据 
	     * @param publicKey 
	     *            甲方公钥 
	     * @param privateKey 
	     *            乙方私钥 
	     * @return 
	     * @throws Exception 
	     */  
	    public static byte[] encrypt(byte[] data, String publicKey,String privateKey) throws Exception {  
	        // 生成本地密钥  
	        SecretKey secretKey = getSecretKey(publicKey, privateKey);  
	        // 数据加密  
	        Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());  
	        cipher.init(Cipher.ENCRYPT_MODE, secretKey);  
	        return cipher.doFinal(data);  
	    }  
	  
	    /** 
	     * 解密<br> 
	     *  
	     * @param data 
	     *            待解密数据 
	     * @param publicKey 
	     *            乙方公钥 
	     * @param privateKey 
	     *            乙方私钥 
	     * @return 
	     * @throws Exception 
	     */  
	    public static byte[] decrypt(byte[] data, String publicKey, String privateKey) throws Exception {  
	        // 生成本地密钥  
	        SecretKey secretKey = getSecretKey(publicKey, privateKey);  
	        // 数据解密  
	        Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());  
	        cipher.init(Cipher.DECRYPT_MODE, secretKey);  
	        return cipher.doFinal(data);  
	    }  
	  
	    /** 
	     * 构建密钥 
	     *  
	     * @param publicKey 
	     *            公钥 
	     * @param privateKey 
	     *            私钥 
	     * @return 
	     * @throws Exception 
	     */  
	    private static SecretKey getSecretKey(String publicKey, String privateKey) throws Exception {  
	        // 初始化公钥  
	        byte[] pubKeyBytes = decryptBASE64(publicKey);  
	        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);  
	        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(pubKeyBytes);  
	        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);  
	        // 初始化私钥  
	        byte[] priKeyBytes = decryptBASE64(privateKey);  
	        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(priKeyBytes);  
	        Key priKey = keyFactory.generatePrivate(pkcs8KeySpec);  
	        KeyAgreement keyAgree = KeyAgreement.getInstance(keyFactory  
	                .getAlgorithm());  
	        keyAgree.init(priKey);  
	        keyAgree.doPhase(pubKey, true);  
	        // 生成本地密钥  
	        SecretKey secretKey = keyAgree.generateSecret(SECRET_ALGORITHM);  
	        return secretKey;  
	    }  
	  
	    /** 
	     * 取得私钥 
	     *  
	     * @param keyMap 
	     * @return 
	     * @throws Exception 
	     */  
	    public static String getPrivateKey(Map<String, Object> keyMap) throws Exception {  
	        Key key = (Key) keyMap.get(PRIVATE_KEY);  
	        return encryptBASE64(key.getEncoded());  
	    }  
	  
	    /** 
	     * 取得公钥 
	     * @param keyMap 
	     * @return 
	     * @throws Exception 
	     */  
	    public static String getPublicKey(Map<String, Object> keyMap) throws Exception {  
	        Key key = (Key) keyMap.get(PUBLIC_KEY);  
	        return encryptBASE64(key.getEncoded());  
	    }  
}
